Implication of vector characteristics of Phlebotomus argentipes in the kala-azar elimination programme in the Indian subcontinent

Authors:

Rajib Chowdhury, Vijay Kumar, Dinesh Mondal, Murari Lal Das, Pradeep Das,
Aditya Prasad Dash & Axel Kroeger

Background:

Visceral leishmaniasis (VL), also known as kala-azar in the Indian sub-continent (ISC), is a major
public health concern in Bangladesh, India, and Nepal, where it is caused by Leishmania donovani transmitted
by the sand fly Phlebotomus argentipes. Various ecological parameters including air temperature, rainfall, wind
speed, relative humidity, soil moisture, pH, and organic carbon are known to influence the oviposition of female
sand flies, as well as the survival and development of larvae. However, more detailed knowledge on vector
behavior, such as biting times, breeding places, and preferred hosts are needed to design optimal evidencebased
vector control interventions.

Methods:

In order to facilitate rational decisions regarding VL vector control, a systematic review was conducted
to identify the prevailing practice and knowledge gaps in relation to vector bionomics and behavior. Search terms
included ‘sand fly bionomics’, ‘habitat’, and ‘visceral leishmaniasis/kala-azar vector control’ using the Boolean
operator AND to identify the country of interest, namely: Bangladesh, India, and Nepal. Both PubMed and Google
search engines were used. Additional unpublished documents in the three countries were also analyzed.

Results:

Information on the life cycle of VL vectors, their breeding behavior, infection rate with L. donovani, feeding
behavior, and seasonal variation are useful for designing vector control operations. Unfortunately, none of the
studies on the life cycle of P. argentipes was conducted in field settings of the ISC, so the publications from other
locations had to be used for determining the duration of life cycle and development from egg to adult. However,
information about breeding places, seasonal variation of vector densities, and 47 out of the selected 51 papers
are available from the ISC and can be used for intelligent design of control operations.

Conclusion:

Vector control services should undertake routine insecticide resistance monitoring and adapt indoor
residual spraying rounds to the seasonality of vector densities. Further research is needed on potential animal
reservoirs for L. donovani, on the breeding habitat, and life cycle of sand flies in the ISC.